A polyarylene sulfide (hereinafter abbreviated to “PAS”) such as polyphenylene sulfide (hereinafter abbreviated to “PPS”) has excellent heat resistance and chemical resistance, and is widely used for electric/electronic components, car components, water heater components, fibers, and films. Such a PAS usually has drawbacks that it has a low molecular weight and components obtained by forming the PAS have poor impact strength and are inferior in compatibility with the other resins and tight adhesion with other members when formed into moldings.
As a method for improving an impact strength of the PAS, there is a known technology for improving reactivity with a silane-based coupling agent by selectively introducing a reactive functional group such as a carboxyl group into the molecular end of the PAS (refer to Patent Document 1). Although it is sufficiently recognized that the PAS obtained by the method has an effect of improving reactivity of the molecule end of the PAS, it is difficult to obtain a polyarylene sulfide having a higher molecular weight since a reactive functional group is introduced into the end by termination of the polymerization on the way, and the technology fails to sufficiently improve an impact strength and also imposes restriction on the design of the polymer structure.
As a technology for enhancing compatibility with the other resin by introducing a carboxyl group into the PAS, for example, there is known a method in which a PAS and a carboxyl group-containing modifier are melt-kneaded to produce a carboxyl group-containing PAS (refer to Patent Document 2). However, since the method simply melt-kneads the PAS and the modifier, it fails to introduce the carboxyl group in a given position of the molecular structure of the PAS, and thus polymer design cannot be conducted according to the purposes and applications.
Similarly, as a technology for introducing a carboxyl group into a PAS, there is a known technology as a method for producing a carboxyl group-containing PAS as a precursor of an ionomer resin, which comprises subjecting sodium hydrosulfide hydrate and sodium hydroxide to a dehydration treatment using N-methylpyrrolidone as a solvent; and reacting them with dichlorobenzoic acid, dichlorobenzene, and a sulfiding agent (refer to Patent Document 3). However, since the reactivity of the dichlorobenzoic acid itself is low in the technology, the molecular weight decreases and the unreacted dichlorobenzoic acid remains in the reaction product, and thus sufficient effects of improving the compatibility and tight adhesion are not exerted. In addition, it is substantially impossible to introduce the carboxyl group into a given position.
Thus, when an acid group such as a carboxylic group is introduced into a molecular structure of the PAS, there existed a problem that a decrease in a molecular weight arises and it is impossible to sufficiently introduce the carboxyl group into the PAS molecular structure because of low reactivity of the carboxylic group-containing compound. Furthermore, it was impossible to introduce an acid group into a given position of the polymer structure according to the purposes and applications since there is large restriction on design when the acid group is introduced into the polymer structure.
[Patent Document 1]    Japanese Unexamined Patent Application, First Publication No. 2001-181394
[Patent Document 2]    Japanese Unexamined Patent Application, First Publication No. Hei 5-170907
[Patent Document 3]    Japanese Unexamined Patent Application, First Publication No. Hei 8-283413